Articles

Development of On-Site Test Methods to Evaluate Fiber Stability in UHPC

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Abstract

While it is generally expected that UHPC is self-consolidating, it is often challenging to achieve the desired workability, which creates an obstacle to the wide adoption of this new material. The viscosity of Ultra-High-Performance Concrete (UHPC) is a major factor in maintaining uniform fiber distribution, especially in deep components, as the density of steel fibers is much higher than that of the paste, which makes it prone to segregation. Currently, fresh UHPC workability largely relies on the flow (spread) test, which is insufficient to evaluate fiber stability. Furthermore, due to the lack of effective quality control of UHPC during production and construction, different levels of fiber segregation are often observed in highly flowable UHPC mixtures, which could lead to significant concern in the structural performance of cast-in-place or precast concrete components. This paper presented a preliminary study of developing a set of onsite fresh and hardened UHPC test methods to evaluate the fiber stability of UHPC. Results showed that methods such as the Visual Stability Index (VSI), mini-V-funnel, and falling ball test could successfully assess fiber stability in fresh UHPC. In addition, besides the Hardened Visual Stability Index (HVSI), a surface electric resistivity meter could be an effective tool for the in-situ evaluation of fiber distribution in hardened UHPC products. The development of onsite QA/QC methods and assurance of appropriate fiber stability is essential for having a quality product to ensure that fibers are well-distributed as assumed in design and avoid disposal of costly products.

Keywords: UHPC, flow, fiber, stability, segregation, workability

How to Cite:

Aitbayeva, A., Morcous, G. & Hu, J., (2023) “Development of On-Site Test Methods to Evaluate Fiber Stability in UHPC”, International Interactive Symposium on Ultra-High Performance Concrete 3(1): 52. doi: https://doi.org/10.21838/uhpc.16674

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